Lecture Human anatomy and physiology - Chapter 2: Chemistry comes alive (part b)
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Part B:
Chemistry Comes Alive:
Inorganic compounds
Water, salts, and many acids and bases
Do not contain carbon
Organic compounds
Carbohydrates, fats, proteins, and nucleic acids
Contain carbon, usually large, and are covalently bonded
60%–80% of the volume of living cells
Most important inorganic compound in living
organisms because of its properties
High heat capacity
◦Absorbs and releases heat with little temperature change
◦Prevents sudden changes in temperature
High heat of vaporization
◦Evaporation requires large amounts of heat
◦Useful cooling mechanism
Polar solvent properties
◦Dissolves and dissociates ionic substances
◦Forms hydration layers around large charged molecules,
e.g., proteins (colloid formation)
◦Body’s major transport medium
+
–
+
Water molecule
Salt crystal
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Ions in solution
Figure 2.12
Reactivity
◦A necessary part of hydrolysis and dehydration synthesis
reactions
Cushioning
◦Protects certain organs from physical trauma, e.g.,
cerebrospinal fluid
Ionic compounds that dissociate in water
Contain cations other than H+ and anions other
than OH–
Ions (electrolytes) conduct electrical currents in
solution
Ions play specialized roles in body functions (e.g.,
sodium, potassium, calcium, and iron)
Both are electrolytes
◦Acids are proton (hydrogen ion) donors (release H+ in
solution)
HCl H+ + Cl–
Bases are proton acceptors (take up H+ from
solution)
◦NaOH Na+ + OH–
OH– accepts an available proton (H+)
OH– + H+ H2O
Bicarbonate ion (HCO3–) and ammonia (NH3) are
important bases in the body
Acid solutions contain [H+]
◦As [H+] increases, acidity increases
Alkaline solutions contain bases (e.g., OH–)
◦As [H+] decreases (or as [OH–] increases), alkalinity
increases
pH = the negative logarithm of [H+] in moles per
liter
Neutral solutions:
◦Pure water is pH neutral (contains equal numbers of H+
and OH–)
◦pH of pure water = pH 7: [H+] = 10 –7 M
◦All neutral solutions have a pH 7
Acidic solutions
◦ [H+], pH
◦Acidic pH: 0–6.99
◦pH scale is logarithmic: a pH 5 solution has 10 times
more H+ than a pH 6 solution
Alkaline solutions
◦ [H+], pH
◦Alkaline (basic) pH: 7.01–14
Concentration
(moles/liter)
[OH–]
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Examples
[H+]
pH
100
10–14
14
1M Sodium
hydroxide (pH=14)
10–1
10–13
13
Oven cleaner, lye
(pH=13.5)
10–2
10–12
12
10–3
10–11
11
10–4
10–10
10
10–5
10–9
9
10–6
10–8
8
10–7
10–7
7
10–8
10–6
6
10–9
10–5
5
10–10
10–4
4
10–11
10–3
3
10–12
10–2
2
10–13
10–1
1
10–14
100
0
Household ammonia
(pH=10.5–11.5)
Household bleach
(pH=9.5)
Egg white (pH=8)
Neutral
Blood (pH=7.4)
Milk (pH=6.3–6.6)
Black coffee (pH=5)
Wine (pH=2.5–3.5)
Lemon juice; gastric
juice (pH=2)
1M Hydrochloric
acid (pH=0)
Figure 2.13
pH change interferes with cell function and may
damage living tissue
Slight change in pH can be fatal
pH is regulated by kidneys, lungs, and buffers
Mixture of compounds that resist pH changes
Convert strong (completely dissociated) acids or
bases into weak (slightly dissociated) ones
◦Carbonic acidbicarbonate system
Contain carbon (except CO2 and CO, which are
inorganic)
Unique to living systems
Include carbohydrates, lipids, proteins, and
nucleic acids
Many are polymers—chains of similar units
(monomers or building blocks)
◦Synthesized by dehydration synthesis
◦Broken down by hydrolysis reactions
(a) Dehydration
synthesis
Monomers are joined by removal of OH from one monomer
and removal of H from the other at the site of bond formation.
Monomer 1
+
Monomer 2
Monomers linked by covalent bond
(b) Hydrolysis
Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other.
Monomer 1
+
Monomer 2
Monomers linked by covalent bond
(c)
Example reactions
Dehydration synthesis of sucrose and its breakdown by hydrolysis
Water is
released
+
Water is
consumed
Glucose
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Fructose
Sucrose
Figure 2.14
Sugars and starches
Contain C, H, and O [(CH 0) ]
2
n
Three classes
◦Monosaccharides
◦Disaccharides
◦Polysaccharides
Functions
◦Major source of cellular fuel (e.g., glucose)
◦Structural molecules (e.g., ribose sugar in RNA)
Simple sugars containing three to seven C atoms
(CH 0)
2
n
(a) Monosaccharides
Monomers of carbohydrates
Example
Example
Hexose sugars (the hexoses shown
Pentose sugars
here are isomers)
Glucose
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Fructose
Galactose
Deoxyribose
Ribose
Figure 2.15a
Double sugars
Too large to pass through cell membranes
(b) Disaccharides
Consist of two linked monosaccharides
Example
Sucrose, maltose, and lactose
(these disaccharides are isomers)
Glucose
Fructose
Sucrose
PLAY
Glucose
Glucose
Maltose
Galactose Glucose
Lactose
Animation: Disaccharides
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Figure 2.15b
